Expandable broadheads that mate with an arrow and include a plurality of blades that are shiftable between a retracted inflight position and an extended penetrating position are exemplified in reissue Pat. RE 44,144 reissued on Apr. 9, 2013, the contents of which are incorporated herein by reference.
In this patent a broadhead having a number of expandable blades is disclosed in which the broadhead is manufactured with a central ferrule which contains moveable blades within the ferrule that are extended outwardly upon impact of the broadhead with a target. Note that the blade cutting surfaces point out when in flight or deployed. In one embodiment in the retracted position the blades are contained within a blade recess in the form of a slot or a groove within the broadhead ferrule and move outwardly by translating along the surfaces of the slot to cam the blades to an extended position. It will be noted that this type of expandable broadhead and indeed many others provide for the blades housed within slots in a solid ferrule.
While these broadheads are exceptionally useful in bowhunting and indeed in bowfishing, on occasion the blades will stick or bind in the ferrule slots such that the blades do not extend upon impact. Moreover, due to the relatively large bullet-like tip of the ferrule the penetration of the arrow into the target is limited by the diameter of the tip. The result is that penetrating power of these broadheads is unnecessarily limited.
Moreover, for some expandable broadhead configurations the expandable blades may extend during flight resulting in poor aiming accuracy and causing the arrow to go off course both due to aerodynamic turbulence and due to the severe effect of crosswinds on the broadhead structure itself.
While the aforementioned expandable broadheads contain at least a portion of the expandable blades within a solid ferrule, as illustrated in U.S. Pat. No. 4,615,529 extensible blades are pivoted on the fixed blades of a broadhead. However, as can be seen in this patent the extensible blades are limited to pivoting deployment from a forward pivoted location with the cutting edges pointing toward the ferrule. This means that the blades are pivoted on the fixed arrow blade such that rather than moving from an inflight retracted position running aft, they extend from a forward facing position. This means that the blades on the fixed blades pivot from a forward collapsed position to a transverse final position. As such the blades are not cammably deployable. This type of configuration is subject to unintentional opening of the pivoted blades due to the air flow over the arrow in flight, thus decreasing penetrating power as well as causing aerodynamic instabilities which cause the arrow to go off track, to say nothing of crosswind and turbulence effects on the arrow flight path. If the blades are sufficiently constrained that they do not deploy early, then the energy necessary to cause them to pivot to the cutting position is significant in that it greatly reduces the penetration of the arrowhead. This type of broadhead is commonly referred to as a, “over the top expandable” broadhead.
This type of configuration in which a fixed arrow blade is provided with over the top deploying secondary blades is also exemplified by the SteelForce Phat Head SOB4-blade broadhead that is presently available. This broadhead has a fixed blade structure to which there are pivoted forward facing moveable blades having tips which extend outwardly past the fixed blade edges. When the arrow enters the target the tips of the moveable blades are pushed outwardly as they enter the target until they rest on a stop at which point they are extended to the full extent. This SteelForce broadhead suffers the same problems as mentioned above with respect to U.S. Pat. No. 4,615,529.
Expandable broadheads are commonly made with either two or more expandable blades. With blades in a configuration with more than two moveable blades, the geometry of the blade attachment point becomes critical. If the pivot location of the blades is close to the primary axis of the ferrule, simultaneous blade rotation allows for the blades to interfere with the motion of one another. This interference is possible both during deployment, as well as during retraction of the arrow from the target. During deployment, if the blades run into one another it can potentially prevent full deployment of the blades. During removal of the arrow from the target, the rotatable blades can interfere with one another and jam in a mid-position, causing a barbing situation which is currently illegal in many jurisdictions. An exemplary broadhead is that mentioned above in U.S. Pat. RE 44,144.
In short there is a necessity to provide an improved expandable broadhead design using a rear deploying expandable blade structure that does not hang up or get stuck in a ferrule slot while at the same time improving penetration capabilities as well as making arrow removal easy after target penetration. Moreover, blade-to-blade interference upon expansion is to be avoided. Most important is the problem of providing a broadhead with rear deployable blades that are made reliable by rotating and translating them on fixed blades such that the cutting power associated with the fixed blades is augmented by the rear deployed blades so as to provide expanded target cutting impact.